Temporary vanes to straighten gas flow in scrubbers

ABSTRACT

A method is provided for flow straightening and sampling gas in the stack of a gas scrubber. In normal operation the gas has a substantially nonaxial flow so as to retain within the stack droplets carried by the gas. A flow straightener having flow straightening panels is assembled in the chamber of the gas scrubber and lifted into the stack. Gas having an axial flow is then sampled. The flow straightener is then removed from the scrubber, and normal operation is resumed.

BACKGROUND OF THE INVENTION

The invention relates to the sampling of gas above a scrubber. Thesesamples are used to determine the particulate concentration in the gasleaving the scrubbers. When permanent straightening vanes are used inscrubber stacks, laminar gas flow occurs resulting in droplets beingcarried out of the stack. These droplets might otherwise impact thewalls and flow out with the scrubber effluent. The methods for samplingparticulate cannot distinguish between dust and other particles in a gasstream and dust in the slurry droplets. This may result in samplingresults being biased high. The removal of the flow straightening deviceallows the swirling of the gases to impact the droplets upon the stackwall. The slurry is thus contained within the scrubber.

The present invention provides a method for the installation oftemporary vanes which when installed provide axial gas flow ideal forthe sampling of particulate. Because the vanes are removed during normaloperation, the amount of droplets leaving the top of the stack issignificantly reduced. This eliminates dirty rain from the stack, apollution hazard itself. More importantly, the few droplets which arecarried out of the stack are substantially without any solids in them ascompared with the significant amount of dust in such particles where thestraightening vanes are permanently installed.

SUMMARY OF THE INVENTION

A method of sampling stack gas from a scrubber stack comprises providinga flow straightener in the chamber of a scrubber having a scrubber stackand a scrubber chamber, said flow straightener comprising a plurality offlow straightening panels and a flow straightening panel support means,

providing upper lifting support means,

lifting said flow straightener from said scrubber chamber into saidscrubber stack while said flow straightener is supported by said upperlifting support means,

sampling gas in said stack,

lowering said flow straightener into said scrubber chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the installation of a flow straightener in accordance withthe present invention.

FIG. 2 shows the flow straightener in its operating position.

DETAILED DESCRIPTION OF THE DRAWINGS

With more particular reference to the Figures, the invention providesfor the sampling of gas in a scrubber stack, coupled with the ease ofinstalling and removing the vanes. FIG. 1 shows a scrubber stack 1 abovea flow straightener 2. The scrubber stack 1 has lower scrubber stackchamber 3 wherein the flow of gas therethrough is nonaxial. The scrubberstack 1 has upper scrubber stack chamber 4 wherein the gaseous flow moreclosely approximates axial flow than the gas flow in the lower scrubberstack chamber 3.

Below the scrubber stack 1 is a gas scrubber 22 defined by scrubberchamber wall 21. Gas scrubbers are provided with manholes through whichoperators may enter and leave the scrubber chamber. In carrying out themethod of the present invention, a flow straightener is brought into thescrubber chamber in separate panels through manhole 23. These panels arethe flow straightener panels 5. The flow straightener panels 5 are fixedto the flow straightener panel support 6 in the scrubber chamber 22. Byproviding a winch 8 and a lifting cable 7, the flow straightener 2 islifted from the scrubber chamber by the lifting cable 7. The liftingcable 7 is supported by the lifting bar 14, the lifting bar 14 isprovided with outer lifting pulley 9 and center lifting pulley 10 bothof which serve to guide the lifting cable 7. The flow straightener 2 isattached to the lifting cable 7 by the lifting cable fastener 11. Theflow straightener 2 is lifted to a position below the lifting bar 14 andabove the safety support port 12. The safety support port 12 is providedwith a safety support port cap 13. By removing the safety support portcap 13 and inserting a safety support bar 20, as shown in FIG. 2, theflow straightener is prevented from falling through the scrubber stack 1if the lifting cable breaks.

By lifting the flow straightener close enough to the lifting bar 14, theanti-rotation tabs 17 may be positioned on either side of the liftingbar to prevent rotation of the flow straightener.

During sampling, the scrubber is operated and the gas from the scrubberpasses past the flow straightener 2 which provides that gas with a flowpattern which is of a more axial nature. By removing the sampling portcap 19 from the sampling port 18, the cross section of the upperscrubber stack chamber 4 may be sampled for gas samples.

After the sampling is completed, the sampling port cap 19 is placed backover the sampling port 18. The flow straightener is lowered back intothe scrubber chamber below the scrubber stack 1. The lifting bar 14 isremoved from the lifting ports 15 and the lifting caps 16 are placedover the lifting ports 15. Of course, prior to lowering the flowstraightener 2, the safety support bar 20 is removed from the safetysupport ports 12 and the safety support port caps 13 are placed over thesafety support ports 12.

The flow straightener is disassembled in the scrubber chamber 22 andremoved through the scrubber chamber manhole 23.

Having thus described the invention by reference to certain of itspreferred embodiments it is respectfully pointed out that embodimentsdescribed are illustrative rather than limiting in nature and that manyvariations and modifications are possible within the scope of thepresent invention. Such variations and modifications may appear obviousand desirable to those skilled in the art upon a review of the foregoingdescription of preferred embodiments.

Having described our invention we claim:
 1. A method of flowstraightening and sampling gas in the stack of a gas scrubber said gasduring normal operation of the scrubber having substantially nonaxialflow so as to retain within said stack droplets carried by said gas,comprising the sequence of steps as follows:(a) providing a plurality offlow straightening panels and a flow straightening panel support meansin the chamber of the gas scrubber, said panels connected to said panelsupport means to form a flow straightener, (b) providing upper liftingsupport means to support said flow straightener, (c) lifting said flowstraightener from said scrubber chamber into said scrubber stack usingsaid lifting support means, (d) providing said flow straightener with alower safety support means to support said flow straightener in saidstack, (e) conveying gas through said scrubber stack and through saidflow straightener, whereby said gas flow is straightened to more closelyapproximate axial flow, (f) sampling gas in said stack after said gashas passed through said flow straightener, (g) removing said safetysupport means and lowering said flow straightener into said scrubberchamber, (h) disconnecting said panels from said panel support means andremoving said panels and panel support means from said scrubber chamber,(i) conveying gas through said scrubber stack in substantially dropletretaining nonaxial flow.
 2. The method of claim 1 wherein said upperlifting support means comprises a lifting bar.
 3. The method of claim 2wherein said upper lifting support means further comprises a liftingcable.
 4. The method of claim 1 wherein said lower safety support meanscomprises a safety support bar positioned beneath said flowstraightener.
 5. The method of claim 1 wherein said flow straightener isprovided with at least two anti-rotation tabs to prevent said flowstraightener from rotating in said stack.